I often leave out the breadcrumb and cheese topping and just put everything into the casserole and cook slowly in a low oven. It's the sort of dish you can leave to cook slowly for hours.
Put everything into the casserole except the topping and cook on a very slow oven all day if necessary.
HEALTH ISSUE - Many people have IBS and don't know what causes it. I have found that red and green peppers cause mine with dire results. I have also read in a cookery book in Spain that if the skins are removed from peppers they are not so troublesome. As yet, I have not had the courage to try this but would be pleased to hear from others with the same allergy.